This invention relates to a novel organophosphorus composition, its method of preparation, and its use in transition metal complex catalyzed reactions. Preferably, this invention relates to a novel organophosphorus composition and its use in transition metal phosphorus ligand complex catalyzed carbonylation processes, preferably, hydroformylation processes.
Carbonylation processes directed to the production of oxygenated products are well known and generally involve reaction of an organic compound with carbon monoxide and often a third reactant, preferably, hydrogen. See, for example, J. Falbe, “New Syntheses With Carbon Monoxide,” Springer Verlag, New York, 1980. Such processes may include the carbonylation of organic compounds, such as olefins, acetylenes, alcohols, and activated chlorides, with carbon monoxide, and optionally, either hydrogen, alcohol, amine, or water, as well as ring closure reactions of functionally unsaturated compounds, e.g., unsaturated amides, with carbon monoxide. One major class of known carbonylation processes comprises the hydroformylation of an olefinic compound with carbon monoxide and hydrogen to produce oxygenated products, such as aldehydes, followed by reduction, if desired, of the aldehyde to alcohol; or reductive amination of the aldehyde to amine; or oxidation of the aldehyde to carboxylic acid; or aldolization of the aldehyde followed by oxidation to hydroxyacid. Amines and oxygenated products, such as alcohols, carboxylic acids, and hydroxyacids find utility in a multitude of applications, including as solvents, surfactants, monomers for the preparation of polymers, and as intermediates in the synthesis of pharmaceuticals and other industrial chemicals.
Carbonylation processes are known to be facilitated by metal-ligand complex catalysts, particularly Group VIII transition metal-phosphorus ligand complex catalysts. Representative art disclosing a variety of hydroformylation catalysts of various triorganophosphine, triorganophosphite, diorganophosphite, and bisphosphite ligands, is found in the following references: U.S. Pat. No. 3,527,809; U.S. Pat. No. 4,599,206; U.S. Pat. No. 4,748,261; and WO-A1-02/00670. Disadvantageously, many of the transition metal-phosphorus ligand complexes disclosed for carbonylation processes exhibit only moderate or low activity for internal olefins and undesirable isomerization of long chain alpha-olefins to internal olefins. Additionally, the ligands disclosed in the art cannot be easily fine-tuned to provide a high selectivity to the desired hydroformylation product.
More recently, D. Selent et al. disclosed in Angewandte Chemie Int. Ed., 2001, 40, No. 9., 1696–1698, that unsymmetrical bidentate phosphorus ligands of formula I, shown hereinbelow, are useful in the hydroformylation of internal olefins.
In formula I, each “t-Bu” represents a tertiary butyl moiety; each R is the same and is either a tertiary butyl or methoxy (—OCH3) substituent; and P* is a phosphorus-containing moiety selected from one of the following three formulas:
Although these prior art ligands are sufficiently active for hydroformylation of terminal and internal olefins, they achieve an unacceptably low normal (N) to iso (I) products selectivity, as measured by an N:I molar ratio typically of only 2/1 to 4/1, when normal aldehydes are the desired products. With such a low N:I selectivity, the yield of the desired normal product is also unacceptably low, at less than about 75 mole percent, when either internal or terminal olefins are used as substrates. These prior art ligands also lack isomerization selectivity when 3-penten-1-ol is used as a substrate, producing 6-hydroxyhexanal in less than about 70 mole percent yield. 6-Hydroxyhexanal is a precursor to caprolactam, which itself is used in the production of Nylon-6.
In view of the above, a search continues in the art to find novel phosphorus ligands that will provide improved activity, improved isomerization selectivity, improved ease of fine-tuning selectivity, and improved stability in carbonylation processes, preferably, hydroformylation processes.